I sympathise!!!
In theory, this tool does work no matter how frustrating your experience with it might be.
The distortions of lenses and the crookedness of composition detract from alignment accuracy. Even Archicad's documents suggest it will need tweaking....
To practice, make a model with some simple faces, render it and then use THAT SAME MODEL as the basis for an additional component. See attached for a practice example - it is from my upcoming Artlantis exercise.... here, the glowing box is inserted into the background image.
With everything computer generated, you eliminate the primary cause of failure. Otherwise, it is simply a matter of methodically transferring the datapoint locales.
Dwight Atkinson